It doesn't take long. I did the test yesterday. I don't undestand exactly how it works. I thought I had passed because the service guy gave me a ssticker on the car for a test in two years. But when I went to do the repairs on my car that the guy recommended, the garage refused to do the repairs saying they couldn't find the components. They told me it was too dangerous to drive and had to send it to the wrecker. So now I have no car. The sticker the guy gave me apparently said the car was unsafe.
If it passes, as my car did in two previous tests, I am not sure where it goes but it is recorded somewhere, you don't do anything. I was five days late this time, my fine was 5000 won, If you don't have car insurance on your car...which i didn't one time, i had a million won fine. But not sure if it would be this high for missing a safety test.
Hope this helps.